Effects of CO2 and electrical stunning methods on selected plasma indices in pigs

The effects of two different stunning methods on selected blood values in pigs at a slaughter plant were monitored. The pigs in Group 1 (n = 20) were stunned by exposure to 85–90% carbon dioxide. The stunning in Group 2 (n = 20) was accomplished with an electric current. Blood samples were taken from the blood draining from the thoracic stick about 5 seconds after bleeding. Plasma cortisol, adrenalin, noradrenalin, ALT, AST, cholesterol, glucose, lactate, LDH-L, total protein and triglycerides were determined. The results of the present study showed that stunning methods affect most of the blood parameters monitored. Significantly higher plasma levels of noradrenalin, ALT, AST, glucose and total protein were found in CO2 stunned pigs, whereas significantly higher plasma levels of cortisol and lactate were found in electrically stunned pigs. If only cortisol levels were considered, CO2 stunning may be favoured over the electrical method as having greater benefits for animal welfare. However, the level of noradrenalin was approximately doubled in CO2 stunned pigs. Further research is needed to determine if this increase occurs before or after the onset of unconsciousness. If it occurs before the onset of unconsciousness, this could be detrimental to pig welfare.